1. Field of the Invention
Invention in general relates to conductivity sensors or cells and particularly to one utilized in the steam path of steam turbines.
2. Description of the Prior Art
It is well known that the impurities in steam used to drive steam turbines in power plants are a corrosion concern. For example, deposition of corrosive salt impurities on steam turbine blades made lead to stress corrosion cracking failure.
Of particular concern is sodium chloride which although dissolved in the superheated steam at low concentrations can, as the steam expands through the turbine, deposit at high concentrations. Near the exit of the low pressure section of the turbine arrangement the steam undergoes an expansion whereby a consequent transition to a wet condition results. The entrained sodium chloride could then form a saturated solution which if deposited upon the turbine rotor blades could lead to corrosion and cracking.
If the location of the salt deposition zone is known, the expansion path of the steam can be shifted in such a way that the induced corrosion damage from the salt solution deposition to a specific component, or components, can be reduced or minimized. An arrangement for shifting this zone is described and claimed in U.S. Pat. No. 4,386,498 and various conductivity sensors for determining the salt deposition zone are described and claimed in U.S. Pat. No. 4,357,576, both applications having the filing date of Oct. 15, 1980 and both being assigned to the same assignee of the present invention.
In various monitoring situations it would be desirable to mount the conductivity sensor directly onto a turbine blade and although various types of sensors and probes are illustrated in the latter application none can conform to a curvilinear surface such as encountered on a rotating or stationary turbine blade. The sensor of the present invenion is about the size of a common postage stamp and can be mounted directly on a curvilinear surface such as a turbine blade in the steam path of a steam turbine.